Saturday, March 26, 2016

Until about 60 million years ago, penguins
soared above the ocean. When they lost the ability to fly, their brains
took a while to catch up.

UT geological sciences graduate student James Proffitt compared 3-D
models of the inside of the earliest-known flightless penguin skull
fossil to the brain shapes of modern penguins. This fossil is about 60
million years old — this penguin was probably alive soon after all
penguins stopped flying.
He expected to find that flightlessness soon affected the ancient
penguin’s brain structure, making it similar to modern penguins.
However, this ancient penguin brain was significantly different from
those of modern penguins, even though they were both flightless. These
differences suggest modern penguin brains may not have evolved until
relatively recently, according to Proffitt.

“It seems like ancient penguins have a lot more in common with other
close diving relatives than they do with modern penguins,” Proffitt
said. “When flightlessness evolved, the changes in the brain that you
see in modern penguins don’t show up until much later.”

Even though it couldn’t fly, this 60-million-year-old penguin’s skull
is more similar to those of present-day birds that can both dive and
fly than to modern flightless penguins. Penguin
neurology took a long time to catch up to flightless behavior, according
to Paul Scofield, the senior curator of natural history at the
Canterbury Museum in New Zealand and co-author of the paper.

“I think this result clarifies that the evolution of penguins was
rapid and that not all elements of the body suddenly became perfectly
adapted to diving,” Scofield said. “Other studies have shown that the
brain’s development lags behind the evolution of the body and this is
certainly the case in this species.”

The evolution of bird brains is easier to study than other types of
animals because bird skulls are closely fitted to the brain. Proffitt’s
work used x-ray computed tomography, or CT scanning, to look inside the
fossilized skull and observe the shape of the brain.

Chris Torres, an ecology, evolution and behavior graduate student
currently in Antarctica studying bird evolution, also uses this CT
scanning method to learn about other types of bird brains from fossils.

“Odd as it may sound, we don’t need brains to study brains anymore,”
Torres said. “This has profound implications for what we can learn from
fossil record, which preserves hard structures like skulls but not soft
tissues like brains. CT has revolutionized the way we study how
bird brains evolve.”

Proffit is interested in studying penguin evolution because,
according to him, they came from a larger group of birds that both fly
and swim, but have since evolved flightlessness.

“They make a really great group to examine this broader evolutionary
idea of how animals respond to such a big change in ecology and what
happens to the rest of their body,” he said.

There is still a lot of research that scientists need to do to
understand the relationship between behavior and brain structure,
according to Proffitt.

“I think it’s a complicated question to try and disentangle how
locomotion effects neurology,” he said. “That’s more of a nuanced
scientific story that isn’t as appealing as a firm answer.”

Wednesday, March 9, 2016

By mimicking the hierarchical microstructure of penguin feathers, researchers have developed an ice-proof insulating material.

Rebecca Tan | March 8, 2016

AsianScientist (Mar. 8, 2016) - Have you ever wondered
how penguins stay warm and dry despite their sub-zero living
environments? Now, researchers from Beihang University have identified
microstructures on penguin feathers responsible for their anti-icing
properties, and have even designed a feather-inspired nanofiber membrane
that can be used as an ice-proof material. Their results have been
published in The Journal of Physical Chemistry C.

Nature is a rich source of inspiration for scientists studying
superhydrophobic, or water-repelling, materials. The rough texture of lotus leaves,
for example, have served as the basis for the design of stain-resistant
clothing. Similarly, the ability of penguins to survive in cold and wet
environments is thought to be due to the superhydrophobic nature of
their feathers which would cause water to slide off before ice has had a
chance to form.

However, superhydrophobic surfaces are known to function poorly
precisely under cold and wet conditions. When humidity is high, the
rough structure of superhydrophobic materials encourages the
condensation of water which quickly turns into a layer of ice, while the
adhesion strength of ice increases at ultralow temperatures, making it
harder for ice that has been formed to slide off.
To better understand the anti-icing properties of penguin feathers, a
team of researchers at Beihang University used scanning electron
microscopy to study the microstructure of feathers from Humboldt
penguins (Spheniscus humboldti).

The feathers had a hierarchical structure, with tiny hooks arranged
at regular intervals on larger barbules that were in turn arranged on
even larger barbs. The hooks formed a wrinkled three-dimensional network
that effectively prevented water from soaking through.

Mimicking the structure of the feathers with polyimide nanofibers,
the researchers developed a membrane where the fibers were spaced a few
micrometers apart. The membrane was shown to be highly water-resistant,
even to microdroplets that had been cooled to -5°C.

“Because of its excellent electrical insulation and
icephobicity, the polyimide nanofiber membrane could be used in
applications such as ice-proof coatings for electrical cables,” Wang
explained.

The researchers plan to further improve the anti-icing properties of
their artificial feathers by studying the packing style of natural
penguin feathers, another decisive factor determining their anti-icing
properties.

Abstract

Sexually
size-dimorphic species must show some difference between the sexes in
growth rate and/or length of growing period. Such differences in growth
parameters can cause the sexes to be impacted by environmental
variability in different ways, and understanding these differences
allows a better understanding of patterns in productivity between
individuals and populations. We investigated differences in growth rate
and diet between male and female Adélie Penguin (Pygoscelis adeliae)
chicks during two breeding seasons at Cape Crozier, Ross Island,
Antarctica. Adélie Penguins are a slightly dimorphic species, with adult
males averaging larger than adult females in mass (~11%) as well as
bill (~8%) and flipper length (~3%). We measured mass and length of
flipper, bill, tibiotarsus, and foot at 5-day intervals for 45 male and
40 female individually-marked chicks. Chick sex was molecularly
determined from feathers. We used linear mixed effects models to
estimate daily growth rate as a function of chick sex, while controlling
for hatching order, brood size, year, and potential variation in
breeding quality between pairs of parents. Accounting for season and
hatching order, male chicks gained mass an average of 15.6 g d-1
faster than females. Similarly, growth in bill length was faster for
males, and the calculated bill size difference at fledging was similar
to that observed in adults. There was no evidence for sex-based
differences in growth of other morphological features. Adélie diet at
Ross Island is composed almost entirely of two species—one krill (Euphausia crystallorophias) and one fish (Pleuragramma antarctica),
with fish having a higher caloric value. Using isotopic analyses of
feather samples, we also determined that male chicks were fed a higher
proportion of fish than female chicks. The related differences in
provisioning and growth rates of male and female offspring provides a
greater understanding of the ways in which ecological factors may impact
the two sexes differently.

Losing the ability to fly gave ancient penguins their unique
locomotion style. But leaving the sky behind didn't cause major changes
in their brain structure, researchers from The University of Texas at
Austin suggest after examining the skull of the oldest known penguin
fossil.

The findings were published in the Journal of Anatomy in February.

"What this seems to indicate is that becoming larger, losing flight
and becoming a wing-propelled diver does not necessarily change the
[brain] anatomy quickly," said James Proffitt, a graduate student at the
university's Jackson School of Geosciences who led the research. "The
way the modern penguin brain looks doesn't show up until millions and
millions of years later."

Proffitt conducted the research with Julia Clarke, a professor in
the Jackson School's Department of Geological Sciences, and Paul
Scofield, the senior curator of Natural History at the Canterbury Museum
in Christchurch, New Zealand, where the skull fossil is from.

The skull is from a penguin that lived in New Zealand over 60
million years ago during the Paleocene epoch. According to Proffitt, it
likely lived much like penguins today. But while today's penguins have
been diving instead of flying for tens of millions of years, the change
was relatively new for the ancient penguin.

"It's the oldest [penguin] following pretty closely after the loss
of flight and the evolution of flightless wing-propelled diving that we
know of," Proffitt said.

The shape of bird skulls is influenced by the structure of the
brain. To learn about early penguin brain anatomy, Proffitt used X-ray
CT-scanning to digitally capture fine features of the skull's anatomy,
and then used computer modeling software to create a digital mold of the
brain, called an endocast.

The researchers thought that loss of flight would impact brain
structure--making the brains of ancient penguins and modern penguins
similar in certain regions. However, after analyzing the endocast and
comparing it to modern penguin brain anatomy, no such similarity was
found, Proffitt said. The brain anatomy had more in common with skulls
of modern relatives that both fly and dive such as petrels and loons,
than modern penguins.

It's difficult to know why modern penguins' brains look different
than their ancestors' brains, Proffitt said. It's possible that millions
of years of flightless living created gradual changes in the brain
structure. But the analysis shows that these changes are not directly
related to initial loss of flight because they are not shared by the
ancient penguin brain.

However, similarities in the brain shape between the ancient species
and diving birds living today suggest that diving behavior may be
associated with certain anatomical structures in the brain.

"The question now is do the old fossil penguins' brains look that
way because that's the way their ancestors looked, or does it have
something maybe to do with diving?" Proffitt said. "I think that's an
open question right now."

###

The research was funded by a grant from the National Science Foundation.